The present invention generally relates to a land grid array and, more particularly, to a method of assembling a land grid array module and an alignment tool for use in the assembling of the land grid array module.
Traditionally, electronic components have been connected to circuit cards (or printed wiring boards) by solder or by pins on the electronic components inserted into plated through holes in the circuit cards. The attachment of an electronic component to a circuit card is generally referred to as xe2x80x9csecond level packagingxe2x80x9d.
With the increasing complexity of circuit cards and their components, reworking of electronic components (i.e., removing defective electronic components from the circuit card and replacing them with nondefective electronic components) has become increasingly necessary, such that reworkability is now an extremely important design criterion.
In response to the demands of component rework, the land grid array (hereafter LGA) concept has been developed. Generally speaking, in LGA technology, contacts on the electronic component are mechanically held against mating pads on the circuit card. To facilitate the electrical connection between the electronic component and circuit card, an LGA socket or interposer may be placed between the electronic component and circuit card.
A typical land grid array (hereafter LGA) design is illustrated in Kastberg et al. U.S. Pat. No. 6,191,480, the disclosure of which is incorporated by reference herein. In Kastberg et al., a semiconductor device 50 is joined to a substrate 20 having contact pads which are to make contact with contact pads on a circuit card (not shown). Contact between the contact pads on the substrate 20 and the contact pads on the circuit card are made through LGA socket 15 (also called an LGA interposer) which is placed on the circuit card. Substrate 20 is mechanically held in the LGA socket 15 by pressure plate 10.
Other art relating to LGA technology includes:
Samaras et al. U.S. Pat. No. 5,991,161, the disclosure of which is incorporated by reference herein, discloses an LGA interposer for multi-chip applications.
McHugh et al. U.S. Pat. No. 5,984,693, the disclosure of which is incorporated by reference herein, discloses a contact embodiment for an LGA socket.
Pai et al. U.S. Pat. No. 5,953,816, the disclosure of which is incorporated by reference herein, discloses a process for making an interposer for an LGA.
Volz et al. U.S. Pat. No. 5,302,853, the disclosure of which is incorporated by reference herein, discloses a frame and latching mechanism for mechanically attaching an LGA package to a circuit card.
To place the LGA socket on the circuit card, alignment pins on the underside of the LGA socket must be aligned into mating holes in the circuit board. During the alignment operation, there is the tendency to press down on the LGA socket and wipe the bottom side of the LGA socket against the circuit board which may result in a smearing of the contacts in the LGA socket. Smearing can result in defective contact points which can lead to bridging between the contact pads or to opens. Either of these circumstances is undesirable.
To address this alignment problem, there is a need for an alignment method to align the LGA socket and the circuit card.
Accordingly, it is a purpose of the present invention to have a method to align an LGA socket (with an electronic component) with a circuit card.
It is another purpose of the present invention to have such a method to align an LGA socket with a circuit card that is easy to accomplish and that does not damage the LGA socket or any of the other mating electronic components.
These and other purposes of the invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.
The purposes of the invention have been achieved by providing, according to a first aspect of the present invention, a method of assembling a land grid array module comprising a land grid array card, land grid array socket and substrate, the method comprising the steps of:
(a) obtaining an alignment tool comprising a nest and guide tool;
(b) inserting the land grid array socket and substrate into the nest;
(c) inserting the guide tool into the nest;
(d) picking up the guide tool, substrate and land grid array interposer from the nest;
(e) placing the guide tool, substrate and land grid array socket onto the land grid array card; and
(f) removing the guide tool.
According to a second aspect of the invention, there is provided an alignment tool for assembling a land grid array comprising:
a nest comprising a body having a plurality of apertures and a plurality of locating portions for accurately locating a land grid array socket; and
a guide tool comprising a planar body having a plurality of guide pins and a plurality of cutout portions;
wherein, in operation, a land grid array socket is placed in the nest and accurately located therein by the nest locating portions, a substrate is placed on the land grid array socket, and the guide tool is releasably joined to the nest by inserting the guide pins into the apertures of the nest, the cutouts of the guide tool allowing one to simultaneously grip the land grid array socket, substrate and guide tool planar body.